The purpose of this project is to determine the role of hormones and other factors in the regulation of protein turnover in skeletal muscle. An isolated perfused preparation of rat hemicorpus consisting predominantly of skeletal muscle has been developed in this laboratory and studies during the past grant period have demonstrated the suitability of the preparation as a model for investigating the regulation of skeletal muscle metabolism. The regulation of protein synthesis and degradation, the regulation of net amino acid release, and the role of fatty acids in regulating protein metabolism will be investigated. An attempt will be made to elucidate the mechanisms involved in the effects of insulin to facilitate peptide-chain initiation and inhibit protein degradation. The possibility that the effect of the hormone on proteolysis involves alterations in lysosomal proteases will be investigated. Effects of other hormones on protein metabolism will be localized to specific steps in the pathway of synthesis and degradation. In preliminary studies it has been found that fatty acids do not affect protein synthesis or insulin-stimulated glucose uptake in this preparation. Since palmitate stimulates protein synthesis and inhibits glucose uptake in heart muscle, the role of fatty acids in regulating protein metabolism in skeletal muscle may be different. This preparation will also permit a study of the role of hormonal regulation of amino acid release from peripheral tissues in the control of hepatic gluconeogenesis and of the contribution of skeletal muscle to the altered amino acid metabolism of diabetes and other hormonal and nutritional disorders.